With the increasing size of the integrated circuit, the current fate of Moore's Law seems to be mostly focused on the improvement of silicon transistors. However, there are gradually researchers starting to start from other components: for example, connect the various transistors to form a complex circuit of copper. And graphene in which played a key role. lm3s9d90-iqc80-a1
In order to improve performance, integrated circuit density continues
to increase, and in the same area of the chip which plugged into more
transistors, it means that more lines need to connect them. In 2000,
the first group of copper interconnects was produced, with 1 km of
copper per square centimeter; but today's 14 nm node processors were
able to contain 10 km of copper in the same area.
Now the more sophisticated the chip, the copper wire becomes thinner,
the resistance also increases, but has to carry more current to speed
up the switching speed, improve performance, so will produce
electromigration (Electromigration) phenomenon. The electrons of the
copper wire will transfer the kinetic energy to the metal ions, so that
the ions move toward the electric field in the opposite direction and
gradually migrate, resulting in the diffusion and loss of the atoms of
the copper wire, resulting in a short circuit.
The current solution is to set the copper wire in the trenches, and
the inner walls of the trenches cover tantalum nitride with a thickness
of 2 nm, which prevents the escape of copper. But this way top up to 10
nm and 7 nm nodes. As the process continues to shrink, the inner wall of
2 nm will become too thick. s50240
At the IEEE International Conference on Electronic Equipment, held in
San Francisco last December, H.-S. Philip Wong from Stanford's
electrical engineer and his team found that polystyrene was used to
solve the problem of electromigration Phenomenon, and reduce the
resistance. Wong said that although researchers have already studied
other linings that may block electromigration, including ruthenium and
magnesium, graphene can be thinner than any material. In addition, the
semiconductor industry in fact try to avoid looking for new materials to
spend too much time, but now the situation, if the copper life can no
longer continue, you must use new materials (such as cobalt) to replace.
Stanford's team is currently working with Lam Research Corp. and
Zhejiang University in China to test composite material routing to allow
graphene to be produced online from copper. Corning has developed a
special manufacturing method, will not damage the rest of the chip at
the temperature (below 400 ℃), this coating of graphene composite
material to suppress the effect of electromigration is the general
copper 10 times , And only half the resistance.
Moore's Law to go on, in addition to the transistor, the potential is
even the memory, lines and so have to join the ranks of improvement,
and the role of graphene or will be more eaten.